1. Field of the Invention
The invention relates to a frequency multiplex system for single side-band transmission of telephone channels converted in steps into the transmission position. These frequency multiplex systems are also called carrier frequency systems and have in most cases a construction in which the individual 4 kHz wide telephone channels are converted by carriers that represent whole-numbered multiples of 4 kHz into the transmission position.
2. Description of the Prior Art
According to the recommendations of the CCITT (Comite Consultatif International Telephonique et Telegraphique) the frequency plans of most wide-band carrier frequency systems find their frequency schedules based on a base primary group of 60 to 108 kHz with 12 telephone channels arrayed one adjacent another. Five of these primary groups are combined as a group into a 60-channel group, the base secondary group of 312 to 552 kHz. A further grouping can be achieved, for example, by the means that five base secondary groups are converted into a base tertiary group including 300 channels in the frequency position 812 to 2044 kHz. The carriers with which the individual channels are converted in one or more stages into the base primary group position and the carriers for the further conversion into the base tertiary group position are in each case whole-numbered multiples of 4 kHz.
The invention proceeds from the consideration that not only pure telephone channels, but also television-telephone or videophone channels should be transmitted on a frequency multiplex system basis. As long, however, as a long distance communication network designed especially for videophone transmission does not exist, it is logical, as is the case already for example with respect to data transmission, to use available frequency multiplex systems for the long distance traffic or videophone channels.